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Date: Fri, 10 Apr 2015 18:54:07 -0700
From: Martin KaFai Lau <kafai@...com>
To: <netdev@...r.kernel.org>
CC: Hannes Frederic Sowa <hannes@...essinduktion.org>,
<kernel-team@...com>
Subject: [RFC PATCH 04/10] ipv6: Only create RTF_CACHE routes after encountering pmtu exception
This patch creates a RTF_CACHE routes only after encountering a pmtu exception.
After ip6_rt_update_pmtu() has inserted the RTF_CACHE route to the fib6 tree,
the rt->rt6i_node->fn_sernum will be bumped which fails the ip6_dst_check() and
triggers a relookup.
Signed-off-by: Martin KaFai Lau <kafai@...com>
Reviewed-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
net/ipv6/route.c | 92 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 49 insertions(+), 43 deletions(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f753a67..1b57bc9 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -907,16 +907,13 @@ static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
struct flowi6 *fl6, int flags)
{
struct fib6_node *fn, *saved_fn;
- struct rt6_info *rt, *nrt;
+ struct rt6_info *rt;
int strict = 0;
- int attempts = 3;
- int err;
strict |= flags & RT6_LOOKUP_F_IFACE;
if (net->ipv6.devconf_all->forwarding == 0)
strict |= RT6_LOOKUP_F_REACHABLE;
-redo_fib6_lookup_lock:
read_lock_bh(&table->tb6_lock);
fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
@@ -935,46 +932,12 @@ redo_rt6_select:
strict &= ~RT6_LOOKUP_F_REACHABLE;
fn = saved_fn;
goto redo_rt6_select;
- } else {
- dst_hold(&rt->dst);
- read_unlock_bh(&table->tb6_lock);
- goto out2;
}
}
dst_hold(&rt->dst);
read_unlock_bh(&table->tb6_lock);
- if (rt->rt6i_flags & RTF_CACHE)
- goto out2;
-
- if (!(rt->rt6i_flags & (RTF_NONEXTHOP | RTF_GATEWAY)) ||
- !(rt->dst.flags & DST_HOST))
- nrt = ip6_pmtu_rt_cache_alloc(rt, &fl6->daddr, &fl6->saddr);
- else
- goto out2;
-
- ip6_rt_put(rt);
- rt = nrt ? : net->ipv6.ip6_null_entry;
-
- dst_hold(&rt->dst);
- if (nrt) {
- err = ip6_ins_rt(nrt);
- if (!err)
- goto out2;
- }
-
- if (--attempts <= 0)
- goto out2;
-
- /*
- * Race condition! In the gap, when table->tb6_lock was
- * released someone could insert this route. Relookup.
- */
- ip6_rt_put(rt);
- goto redo_fib6_lookup_lock;
-
-out2:
rt->dst.lastuse = jiffies;
rt->dst.__use++;
@@ -1144,13 +1107,49 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct rt6_info *rt6 = (struct rt6_info *)dst;
dst_confirm(dst);
- if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) {
+ mtu = max_t(u32, mtu, IPV6_MIN_MTU);
+ if (mtu >= dst_mtu(dst))
+ return;
+
+ if (!(rt6->rt6i_flags & RTF_CACHE) &&
+ (!(rt6->rt6i_flags & (RTF_NONEXTHOP | RTF_GATEWAY)) ||
+ !(rt6->dst.flags & DST_HOST))) {
+ const struct in6_addr *daddr, *saddr;
+ struct rt6_info *nrt6;
+
+ if (skb) {
+ const struct ipv6hdr *iph = ipv6_hdr(skb);
+
+ daddr = &iph->daddr;
+ saddr = &iph->saddr;
+ } else if (sk) {
+ daddr = &sk->sk_v6_daddr;
+ saddr = &inet6_sk(sk)->saddr;
+ } else {
+ return;
+ }
+ nrt6 = ip6_pmtu_rt_cache_alloc(rt6, daddr, saddr);
+ if (!nrt6)
+ return;
+ /* ip6_ins_rt(nrt6) will bump the rt6->rt6i_node->fn_sernum
+ * which will fail the next rt6_check() and invalidate the
+ * sk->sk_dst_cache.
+ */
+ if (ip6_ins_rt(nrt6)) {
+ dst_destroy(&nrt6->dst);
+ return;
+ }
+
+ rt6 = nrt6;
+ dst = &nrt6->dst;
+ } else {
+ rt6 = (struct rt6_info *)dst;
+ }
+
+ if (rt6->rt6i_dst.plen == 128) {
struct net *net = dev_net(dst->dev);
rt6->rt6i_flags |= RTF_MODIFIED;
- if (mtu < IPV6_MIN_MTU)
- mtu = IPV6_MIN_MTU;
-
dst_metric_set(dst, RTAX_MTU, mtu);
rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);
}
@@ -1171,8 +1170,15 @@ void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
fl6.flowlabel = ip6_flowinfo(iph);
dst = ip6_route_output(net, NULL, &fl6);
- if (!dst->error)
+ if (!dst->error) {
+ unsigned char *outer_network_header = skb_network_header(skb);
+ int offset;
+
+ skb_reset_network_header(skb);
+ offset = outer_network_header - skb_network_header(skb);
ip6_rt_update_pmtu(dst, NULL, skb, ntohl(mtu));
+ skb_set_network_header(skb, offset);
+ }
dst_release(dst);
}
EXPORT_SYMBOL_GPL(ip6_update_pmtu);
--
1.8.1
--
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